1. Field of the Invention
The invention relates generally to a system and method for locating failure errors which occur in electronic printed wire assemblies (herein "PWA's"), and, more particularly, to a system for and method of passing external commands to a power on self test (herein "POST") upon detection of an error in POST execution in order to cause particular modules of the POST to again execute thereby narrowing and detecting location of the error in a PWA.
2. Description of the Related Art
A wide variety of electronic devices employ printed wire assemblies. Printed wire assemblies, in general, are intricate networks of integrated electrical paths and devices formed on a stable insulating sheet of material. Today, the process of manufacturing PWA's has been perfected to the point that problems in those devices due to manufacturing are fairly limited. Even so, problems in those devices do continue to arise as a result of imperfect manufacture. Other, and probably more frequent, causes of errors in PWA's include breakdown of materials of those assemblies due to varied stresses, such as certain use and environmental conditions, and, in fact, even the multitude of different environmental conditions to which the assemblies are subjected in use can yield varying results, or errors, due to varying material properties and functions thereof under those different conditions.
Environmental Stress Screening (herein "ESS") is a process by which manufacturers seek to screen their PWA's to determine which PWA's are likely to exhibit errors in the field. In practice, ESS is employed to subject PWA's to conditions in which the PWA's might be expected to be used. For example, a typical ESS process will seek to replicate the conditions of use of a PWA at some point in the life of the PWA. By replicating expected application and field conditions for a specified time duration, latent defects can become detected, and it may be better determined which PWA's are likely candidates for failure problems. This is especially so during a critical 0-60 days after assembly of the PWA when latent problematic conditions may occur at a customer site, which adds cost to rectify.
ESS techniques are helpful in determining which PWA's are likely to fail, however, it is difficult if not impossible to track the source of any failure. This is because tracking the source requires accurate timing of the test through the circuitry of the PWA. For example, certain failures during ESS testing may not allow for an end resulting error code to be externally generated. The failure may occur well into the ESS procedure and cause the PWA to "hang" in a particular state. Once this has occurred, there may be no external error code generated or any generated code may not accurately pinpoint the first source of error occurrence. ESS failure reporting techniques, therefore, have not necessarily been helpful in resolving errors in all cases because either the field conditions can not be exactly duplicated at a repair station or the particular source within any particular PWA of likely errors can not be pinpointed with certainty, due to several environmental conditions which are difficult to duplicate at a repair station, one of which is the temperature at the time of failure.
Most devices employing PWA's are equipped to perform a power on self test (POST) on themselves prior to loading of operating system instructions or other particular desired instructions or functions. The purpose of the POST has generally been to determine, in each instance of use of a device in the field, whether the device will suitably and accurately function in that instance of use. An example of a representative device which employs PWA's is a personal computer. When a personal computer is turned on or an operating system is "booted", the personal computer first executes a POST before performing other functions or operations. The POST is typically part of the basic input/output system (BIOS) of the computer. Generally, the POST will act to check the circuitry and operation of the computer's PWA's in order to assure that, in the particular instance of use, the PWA's will function without error and will operate with proper set-up options given the particular peripherals and internals of the computer.
Though the POST indicates whether the computer will function properly in the particular instance of use, that is typically the only indication from the POST. If the POST indicates an error in a PWA, the computer gives a status and error message. That status and error message does not direct one monitoring the results of the POST to a particular location within the computer at which the error occurred. This is because, in the prior technology, the POST function occurs only once prior to loading further instructions, such as an operating system. Further, though monitoring electronics can detect a PWA failure during a POST routine, there has been no known means to cause the POST or some other mechanism to generate a response indicative of location within the PWA of the failure.
Because ESS techniques lack the ability of accurate replication of field conditions and pinpointing of errors by timing measurements, and because POST techniques lack the ability to trigger the POST or some other mechanism to respond to failures pinpointing locations of error sources, it becomes apparent that a means for performing ESS-like tests under actual field conditions and also pinpointing sources within a PWA of any errors would be a valuable tool for PWA manufacturers and PWA repair centers. The fact that the prior art lacks such a tool is a problem of the prior art.